A fierce Fiona Apple at the Chicago Theatre

“Every single night’s a fight with my brain,” Fiona Apple roared, as if 27 voices were competing for space inside her head. And then she dropped to a near whisper. “I just want to feel everything.”

The singer did all she could to make it so Tuesday at the sold-out Chicago Theatre. She was in warrior mode, flexing Madonna-like biceps and shimmying like Iggy Pop as the music by her four-piece band coursed through her lean frame.

Apple has worked at her own deliberate pace since the ‘90s, releasing four studio albums in that time and rarely touring. Her career started with a multimillion-selling album when she was still in her teens, and she used that success as a license to make more personal, daring music with each subsequent recording.

Her live performances have always bristled with rough edges and the occasional breakdown, but her increased self-confidence and maturity were evident Tuesday. Not that maturity should be confused with mellowing. Indeed, this was the fiercest Apple has ever looked and sounded on a Chicago stage.

She opened with her band playing at blistering volume levels, occasionally drowning her out. But Apple fought back. She slapped her thigh with a drum stick-like object as if willing her voice to pierce the wall of guitar and drums. “Baby, run -- free yourself of me as fast as you can,” she warned.

Her songs described fractious affairs, intimacy gone haywire, a romantic topography littered with casualties. She harnessed all her voices to do these complex relationships justice: She trilled with vibrato-streaked vulnerability, moaned, pleaded and growled. During “Extraordinary Machine,” she channeled the high-pitched warble of a Vaudeville singer.

Apple’s narrators aren’t passive, and they certainly aren’t victims. They’re battle-scarred fighters. If anything, their appetites get the better of them. In “Anything We Want,” she connected the erotic pull of an adult to the unself-consciousness of childhood. Her performance had a similar transparency. She said next to nothing to the audience until the very end, as if emerging from a trance. Until then, she was immersed in the music. Her fists throttled the microphone stand. When she freed herself, her wiry body shook with spasms or tumbled to the stage, a punk-rock contortionist in “Sleep to Dream.”

She pounded a kettle drum with mallets in the high-flying “Daredevil.” When she nearly shouted, “This isn’t about love,” she slammed out percussive chords on a grand piano then let her hands scurry across the keys, a striking visual for the turbulence in the lyrics.

It was a combative, thrilling, sometimes scary performance. Only on the closing cover of Conway Twitty’s 1958 country hit “It’s Only Make Believe” did Apple lower her fists and the volume level, bow her head, and acknowledge that it was time to move on and fight another day.

greg@gregkot.com

Fiona Apple set list Tuesday at Chicago Theatre:

1. Fast As You Can2. On the Bound3. Shadowboxer4. Paper Bag5. Anything We Want6. Get Gone7. Sleep to Dream8. Extraordinary Machine9. Werewolf10. Tymps11. Daredevil12. I Know13. Every Single Night14. Not About Love15. Carrion16. Criminal17. It's Only Make Believe (Conway Twitty cover)